The design of a putter according to the rules of the United States Golf Association require that the shaft or neck or socket of a putter be fixed at any point in the head and need not remain in line with the heel. The axis of the shaft from the top to a point not more than five (5) inches (127 mm) above the sole shall diverge in the toe-heel plane from the vertical by at least ten (10) degrees in relation to the horizontal line determining the length of the head.
The clubhead of the putter provides that the length of the clubhead shall be greater than the breath. These measurements are made on horizontal lines between the vertical projections of the extremities when the clubhead is grounded in its normal address position. The rules further permit that only for putters can furrows or runners extend into the face.
Conventional putters have a flat face which when striking the ball, especially on a long putt, causes the ball to skid. The skidding causes a loss of control of the ball since the ball can jump off the ground especially on a long putt. Skidding can amount to 20% of the distance to the hole in long putts.